NASA is building a giant rocket called the Space Launch System to send humans to Mars. In part 4 of our Horizon Goal series, we recap the messy tangle of politics and engineering that led to the vehicle's creation in 2011.

The Rosetta mission will end tomorrow when the spacecraft impacts the comet. ESA took advantage of the presence of hundreds of members of the media to put on a showcase of Rosetta science. If there’s one thing I learned today from all the science presentations, it’s this: Rosetta data will be informing scientific work for decades to come.

Nine years ago today, Dawn set sail on an epic journey of discovery and adventure. The intrepid explorer has sailed the cosmic seas and collected treasures that far exceeded anything anticipated or even hoped for.

As OSIRIS-REx speeds away from Earth, it’s been turning on and testing out its various engineering functions and science instruments. Proof of happy instrument status has come from several cameras, including the star tracker, MapCam, and StowCam.

SpaceX's plans to colonize Mars differ considerably from NASA's Journey to Mars ambitions. But direct comparison is difficult. SpaceX is able to wipe the slate clean and start fresh with a bold new approach to humans in space. NASA has no such luxury, and must use existing pieces and people to make their goals a reality.

After much anticipation, Elon Musk revealed his plans to colonize Mars. Here are the details, some questions yet to be answered, and a few thoughts on how this could change the way we think about human spaceflight.

New scientific findings add to the evidence that Europa is spouting its liquid ocean into space. NASA has a mission to Europa in the works, but it wouldn't launch for at least a decade. Congress can make it faster, but it all depends on whether they can pass a budget this year.

We're back from our #RocketRoadTrip through four states with NASA field centers involved in the agency's Journey to Mars program. We'll be sorting through our material for quite some time, but meanwhile, here are five key things we learned.

The astronomy world is abuzz today because of ESA's announcement of the first release of data from the Gaia mission. Gaia is a five-year mission that will eventually measure the positions and motions of billions of stars; this first data release includes positions for 1.1 billion of them, and proper motions for 2 million.